The present invention relates broadly to control systems associated with ink jet printers and, more particularly, to an automatic print gap adjustment assembly to adjust the gap between a printhead and print media.
Modem ink jet printers typically offer high quality printing results. One of the factors that determines the quality of the print produced by an ink jet printer is the gap or spacing between the printhead and the print media. Print quality can be enhanced if the print gap is adjusted to compensate for different media thicknesses. Typically, the adjustment will provide a first print gap for single sheet use and a second print gap for envelope use with the second print gap being wider than the first print gap. The adjustment of the print gap can be accomplished by physically moving the printhead closer or farther away from the media.
Typically the print gap adjustment will be accomplished by manual manipulation of a lever on the printer that the user must operate. The lever usually provides a first position for a first print gap and a second position for a second print gap. Automatic print gap adjustment has typically been accomplished using complex mechanical devices involving eccentric bearings. Accordingly, there exists a need for an inexpensive automatic gap adjustment that requires no user intervention and provides consistent, accurate results.
It is accordingly an object that the present invention to provide an assembly for automatically adjusting the print gap in an ink jet printer that is mechanically simple and relatively inexpensive to accomplish.
It is another object of the present invention to provide such a print gap adjustment assembly that is accurate and reliable.
To those ends, the present invention is directed to an apparatus for adjusting a print media gap on a printer having a movable printhead carriage configured for selective lateral displacement thereof for controlled printing on print media. The apparatus includes a support member attached to the printhead carriage and projecting therefrom for supporting the printhead during movement thereof. A guide assembly is mounted to the printer for engagement with the support member and defining a first predetermined path for movement of the printhead therealong at a first print media gap and defining a second predetermined path for movement of the printhead therealong at a second print media gap wherein the first predetermined path and the second predetermined path converge at a path junction. An assembly is provided for directing the support member onto one of the first predetermined path to provide the first print media gap and the second predetermined path to provide the second print media gap dependent on a selected print media.
Preferably, the directing assembly includes a first path junction, where the first predetermined path and the second predetermined path converge. The first path junction is disposed at a first end of the guide assembly for movement of the support member from the first predetermined path to the second predetermined path. The directing assembly also includes a second path junction where the first predetermined path and the second predetermined path converge. The second path junction is disposed at a second end of the guide assembly for movement of the support member from the second predetermined path to the first predetermined path.
It is further preferred that the assembly for directing includes a first wall member disposed along the first predetermined path at the first path junction for directing the support member from the first predetermined path to the second predetermined path, and a second wall member disposed along the second predetermined path at the second path junction for directing the support member from the second predetermined path to the first predetermined path.
It is preferential that the directing assembly includes an arrangement associated with the printer for selectively moving the support member to the first path junction for contact with the first wall member to move the support member from the first predetermined path to the second predetermined path for changing a first print gap spacing to a second print gap spacing and for selectively moving the support member to the second path junction for contact with the second wall member to move the support member from the second predetermined path to the first predetermined path, thereby returning the print gap spacing to the first print gap spacing.
The arrangement for moving the support member preferably includes a preprogrammed microcomputer configured for controlling movement of the support member toward the first path junction when changing from a print media having a first thickness to a print media having a second thickness, wherein the second thickness is greater than the first thickness, and the preprogrammed microcomputer may be configured for controlling movement of the support member toward the second path junction when changing from the second print media to the first print media.
It is preferred that the support member includes a wheel rotatebly mounted to an axle and selectively laterally displacable thereon wherein the wheel selectively travels along one of the first predetermined path and the second predetermined path during printing. Preferably, the wheel is configured for abutment with the first wall member and the second wall member for lateral displacement along the axle during a transition between the first predetermined path and the second predetermined path.
It is further preferred that the guide assembly includes a first guide ridge disposed at the first path junction for enhancing the ability of the wheel to remain in the second path after a transition from the first predetermined path to the second predetermined path. The guide assembly may also preferably include a second guide ridge disposed at the second path junction for enhancing the ability of the wheel to remain in the first path after a transition from the second predetermined path to the first predetermined path.
It is further preferred that the guide assembly includes a guide rail having the first predetermined path and the second predetermined path formed therein in a side-by-side relationship. The guide assembly may include a first guide rail having the first predetermined path formed therein and a second guide rail having the second predetermined path formed therein, with the first guide rail and the second guide rail being disposed in a side-by-side relationship.
By the above, the present invention provides a mechanically simple, reliable automatic print gap adjustment assembly that is inexpensive to produce and provides accurate results.